To compare the response of human and rat red cells to DDS-NOH in regard to methe moglobin formation, the production of O2 and thiyl-radical species, sulfhydryl status, skeletal protein changes, echinocyte formation and macrophage ingestion. To determine the effect of inhibition of N- hydroxylation of dapsone on hemotox, the relation between blood levels of DDS-NOH and hemotox in volunteers and in pt receiving dapsone for the treatment of dermatitis herpetiformis, etc., examine the effect of P-450 inhibitors.